The present invention relates to an optical system for reforming of a laser beam having azimuthal polarization.
As is well known, the polarization characteristics of a laser beam have a significant effect upon its ability to process materials. For a laser cutting operation, a beam with circular polarization is highly desirable because it eliminates problems of quality in changes in direction and enables the maintenance of quality and essentially constant speed in the movement of the beam relative to the workpiece.
Most commercially available lasers generate a beam with linear polarization, and a phase shifter will convert the linear polarization to circular polarization. The phase shifter retards by 90° the polarization perpendicular to the plane of incidence which is defined by the incident and reflected beam relative to the parallel polarization.
However, stable-unstable laser resonators such as the Helix-Konus resonator described in European Patent 911,922 emit a laser beam in the shape of a segment of a ring as shown in FIG. 1, and the radiation exhibits polarization vectors which can be described as tangents to a circle or azimuthal. These vectors must be converted to linear for conversion of the beam to one with circular polarization.
Previously, it has been proposed to use specially configured optical elements to reform the laser beam in German Offenlegungsschrift DE 4421 600 A1, filed Jan. 2, 1994. Although this technique effects the reforming of the beam to one with linear polarization, the optics require a very high degree of precision and alignment and, accordingly, are costly.
It is an object of the present invention to provide a novel optical system for reforming a laser beam with azimuthal polarization to one with linear polarization.
It is also an object to provide such an optical system which is readily fabricated and easy to assemble.
Another object is to provide a novel method for reforming a laser beam from one with azimuthal polarization to one with linear polarization